Transformer



' figuration. high .quired. The Fire Underwriters do not approve aninstallation in which the Patented July 6, 1943 UNITED STATES. PATENTOFFICE aszam TRANSFORMER crimes Philippe Boucher, rams, N. 1.,-

signor to Boueher Inventions, m, Washing-1 ton, D. 0., a corporation ofDelaware Application January 2, 1941, Serial No. 372,91: 6 Gains. (01.111-119) This invention relates to electrical transformer apparatus, andmore particularly to transformer apparatus for energizing a negativeload, such as one or more luminescent tubes.

One of the objects of my invention is to provide simple, practical andthoroughly reliable transformer apparatus for the operation of a maximumlength of luminescent tubing with a minimum expense of transformerinvestment a d installation charge.

Another object is the provision of compact, inexpensive and highlyefficient transformer a'p paratus of the character indicated which ispe-.

culiarly adapted to withstand the varyingconditions encountered inactual practical use, including short-circuiting and grounding of thewhole or the parts of the apparatus, without damage to the apparatus andthe consequent necessity for shut-down and replacement or repairs.

A further object is the provision of a transformer apparatus of thecharacter described which lends itself to rapid, efficient andeconomical production employing a minimum of different parts andrequiring a minimum of skill in construction, intallation and repair.

former apparatus connected to a standard single phase, 60 cycle sourceat either 110 volt or 220 volts. The high potential electrical energyhas ordinarily been supplied to the tubes by two separate transformersfor each tube, the transformers being connected inseries and each havingan Another object is to provide a transformer system in which negativeloads of either equal or unequal resistances may be operated from thesame transformer. e

Other objects will be obvious'in part, and in part pointed outhereinafter.

The invention accordingly consists in the combination of elements,features of construction output voltage of about 7,500 volts. In theoperation of a single sign or luminous display. it frequently isnecessary to use a plurality of luminescent tubes and energize thesetube by a way of plurality of transformers, two transformers for eachtube, in order that the energizing potentials may not reach values toground in excess of that specified by the Underwriters. Such aninstallation is expensive, both because of the amount of equipmentinvolved and of the separate labor charge which is made for each unitinstalled. Moreover, a large space is required to accommodate suchequipment.

In certain heretofore known and used transformers, these objects arealleviated somewhat by constructing the secondary winding of thetransformer in two coll sections connected together,

each wound to give a maximum potential of about 7,500 volts andgrounding the inner connection between coil sections. In this manner,the potential across the terminals of a tube may amount to 15,000 volts,for example, while the potential to ground never substantially exceeds7,500

and arrangement of parts, the useful application of which is indicatedin the following claims.

In the accompanying drawing,

- Figure l is a diagrammatic representation of.

my. transformer apparatus as employed in the operation of twoluminescent tubes, and

Figure 2 is a diagrammatic representation of amodifled form of mytransformer apparatus as cent tube. V

As conducive Y to a clearer understanding of certain features of myinvetion, it may be noted at this point that in the operation of aluminescent sign or display employing one or more luminescent gas filledtubes of desired size and conpotential electrical energy is remaximumvoltage to ground at any point. substantially exceeds 1,500

1 jl Ordinarily, the desired high potential electrical energy issupplied. by alternating-current transemployed in the operation of asingle lumines- I volts.

In the ordinary type of transformer, there is danger that one of thecoils will become shortcircuited or grounded and will be destroyed bythe excess current which results. Such short circuiting may be caused bymoist atmospheric conditions or by insects packing themselves in aroundcharredby the a tube .terminal and becoming heat, or by breakage due 'tohigh winds or the shock and vibrations-to which the transformer may besubjected. The excess current which .iiows under short-circuitconditions causes heating of the coils and their insulation to suchadegree that the insulation becomes charred, rendering the coilsuseless, so that the transformer must be shut down for replacement orrepair.

While some heretofore known and used trans formers have providedmagnetic shimts to limit thecurrent in a whole circuit, these designsordinarily do not provide individual protectioh for each cell sectionunless at sacrifice of simplicity. compactness,- emciency and cost.Accordingly, the coil sections a heavy current, and, therefore, arelarger,

heavier and more expensive.

An object of my invention, therefore. is to i frequently are designed tocarry secondary winding coil section.

In the manufacture of heretofore known transformers having core parts ofvarious sizes and configurations, a corresponding number of dies ofdifferent sizes have been required for the manufacture of the variouscore members. These dies are very expensive, and add considerably to thecost of manufacture of the transformers, particularly because a separateset of dies is required for each transformer of diiferentcapacity.

Another object of my invention, therefore, is the provision of a single,compact and eilicient transformer, employing a minimum number ofdifferent parts and requiring a minimum investment of tools andequipmentfor its production, and ail'ording speed and simplicity in assembly andconstruction.

Referring now more particularly to the prac-' an a secondary winding.The core is preferably made of laminated magnetic steel and comprisestwo longitudinal linear members It and it between which are interposedthe F-shaped members II and II with their stems extending inwardly, andshunt pieces I! and is. It will be seen that these core members andassociated shunt pieces form c-shaped magnetic paths around thesecondary coils.

The core members after assembly are pressed together in an arbor pressor other suitable equipmentjto seurre'a ilrm magnetic Joint of lowreluctance between the members. The core members then are held in thatrelationship by steel core bands II and 2|. It is to be noted that shuntpieces I1 and ll are wedged in between the respective stem portions Ilaand lta of the T-shaped members and the adjacent linear bar members IIand II. The desired spacing for the respective airgaps G1 and G: is hadthrough suitable insulation, such as fibre generally indicated at 8. andll.

The shunt pieces may belcmnposed of several laminations placedperpendicularly to the laminations of the main core members. Thisconstruction conveniently permits accurate adjustment of the shunt pathreluctance by adding or taking away ations as maybe necessary to achievethe desired reluctance of the shunt path. .Where desired, it will beunderstood, the

shlmt pieces may be formed of laminations which are parallel-tothe'laminations of the main core I Die primary of my transformer comprisestwo coil sections Pi and P: which aremounted respectively on the members13 and It at opposite ends thereof. The ooils Pi and P: are connected.preferably in series, by the lead II and are from source I! through theleads." and Il. The primary winding 0011 see tions may be connected inparallel, rather than in series, if desired.

The secondary winding comprises coil sections S1 and-Sr which aremounted respectively on the core members l3 and H at ends opposite fromthose on which the primary coil sections are mounted. One terminal ofthe coil S1 is grounded to the core through ametal strip 24 which isheld in firm contact with the core by the core band l9. The otherterminal of the coil S1 is connected by a lead 25 to one terminal of theluminescent tube T1. The other terminal of the tube T1 is grounded as at26. One terminal of the coil S: is likewise grounded to the core througha metal strip 21 which is held in firm contact with the core by the coreband 20. The other terminal of the coil S: is connected by a lead 28 toone terminal of the tube T: whose other terminal is grounded as at 2B.The core itself is grounded as at the ground 28. Two complete secondarycircuits are formed through the leads and ground connections, onecircuit including the coil S1 and tube T1 and the other circuitincluding coil Sr and T2. The current and voltage ratings of the coilsections S1 and S: are dependent upon those of luminescent tubes Ti andT: which they are designed to operate. There is no necessary relationbetween the ratings of the two secondary winding coil sections althoughordinarily they are of approximately the same ratings.

Because the two secondary circuits are entirely separate, the coils S1and S: may be connected either in series or in opposition. In otherwords, it is possible to have the ungrounded terminals of the coils S1and S: to which the leads 25 and 28 respectively are connected, eitherat opposite potentials or at the same potential at any given instant.The arrangement in which the two ungrounded terminals are alwaysapproximately at the same potential is preferable where the tubes T1 andT: are mounted in parallel relationship with their sides close together.Adjacent portions of the respective tubes with such a connection willalways be at substantially the same potential, and therefore, there willbe no tendency for a tube-puncturing dielectric discharge.

In the operation of my transformer, as the electromotive force impressedacross the terminals of the primary coil sections P1 and P: by source I!rises from a zero value, a current begins to flow through the primarywinding. This current generates a magnetomotive force which causes amagnetic flux to flow through the core,

" as indicated in the drawing, for example, by the arrows'during onehalf cycle of the applied electromotive force. This-flux interlinks thesecondary winding coil sections S1 and S: with the primary winding. Thepath of the flux until one of the tubes strikes is in acounter-clockwise direction along the main core path, coursing fromright to left in the" member l3, through member l5, from left to rightin member l4, and through member it back to member i3 during the halfcycle under consideration. It will be understood that during the otherhalf cycle of applied electro-motive force, the flux generated in thecore will follow the same path but in a direction opposite to thatindicated by the arrows.

-The i'iux linking the coil S1 generates an electromotive force in thatcoil, this electrdmotive across the terminals of lead 25 and the groundreaches a value suiliciently tube T1 through the connections. When ithigh to render the gas in the tube T1 1 1mm and conductive, a currentbegins to flow through the tube T1 and its coil 81. The resistance ofthe tube T1 to flow of current being very low when generates amagnetomotive force which opposes the coursing of the main flux andcauses it to seek a path of lower reluctance through the air gap G1,shunt piece I! and core piece stem ia.

. Thus, when current is flowing through cell S1,

and tube T2 is inoperative, during the half cycle under consideration,the major portion of the main flux courses from the right hand end oflinear member l3, asv seen in the drawing. across air gap G1 throughshunt piece 11, stem l5a, the lower main part of member l5, linearmember I4 and member liback to member I3. A minor portion of themagnetic flux then links the primary winding and coil S1. With. thisdecrease influx there is an accompanying decrease in induced potentialso that the secondary current flow is limited to a desired operatingvalue.

Similarly, the flux linking the coil S: generates a voltage in that coilwhich is impressed across the terminals of the tube T2 through the lead28 and the ground connections. When the voltage across the terminals oftube T2 is sufflciently high to ionize the gas in that tube and renderit conductive, a current flows through tube T1 and its coil S2. Thiscurrent likewise is limited to'a desired value through'the action of theshunt core path in diverting the magnetomotive force which bucks themain flux and causes it to seek a path of lower reluctance. Thus, whenthe tube T2 is operative and tube T1 is inoperative, during the halfcycle under consideration. the flux courses in the counter-clockwisedirection from left to right in member it across air'gap G: and throughshunt piece l8, stem or arm I611, the upper part of member l6, member l3and member 15, back to member ll.

Continuing in the cycle of operation; it will. be understood that apoint will be reached where T2 will strike, if T1 has struck first, orT1, in-the event Ta struck first and both tubes then are operating. Atthis point the major portion of the'main flux courses in a path fromright to left in member l3, across air; gap G1 through shunt piece l1,arm lia the lower part of member l5, member l4, air gap G2, shunt pieceI8, arm Ito and the. upper part of member I6 back to member l3; Enoughflux continues to link the coils S1 and S2 to maintain a steady flow ofcurrent through those coils and through the tubes T1 and T2 until theelectromotive force impressed across the terminals of the primarywinding approaches a zero value in continuing through the cycle ofalternations.

When the flux linking the coils S1 and S2 diminishes to such a valuethat the voltage induced in those coils is insufficient to maintain thegas in the tubes T1 and T2 in, an ionized CCU? dition, the tubes becomeextingu shed-and flow 181, a c untermagnetomotive force, is developed.by tha coil which causes the major portion of of current through thetubes and their secondary coils ceases. until the voltage impressedacross the terminals of the primary winding by the source l2 rises to a.value in the opposite direction which is sufficient to again producesuilicient potential in the coils S1 and S2 to ionize the gas in thetubes Ti and T2. At this point, the tubes T1 and T2 The tubes remainextinguished again become conductive and luminous. The current flow intubes and their coil sections is limited to the desired operating valueby the peculiar magnetic .core shunt construction described above. Wherea 60-cycle source is used to energize the primary winding the tubesbecome luminous times per second. Due to persistence of vision, theyappear -to emit a continuous glow of light. 1

While, as a matter of convenience in describing the operation of mytransformer apparatus, the various stages in the operationoi' the twoluminescent tubes T1 and T: and the possibilities attending thisoperation are treated separately, 1

each without special regard to the operating of the other, it will beunderstood that under actual operating conditions both luminescert tubesare rendered conductive and luminous at about the same instant and atabout the same instant become non-conductive and non-luminous. Duringthose brief periods when the tubes are in their non-conductive states,the complete path of the total magnetic flux is along the entire lengthsof linear core members It and H and the main portions of members l5 andi6 eflecting the closure of the magnetic circuit. During those periodswhen tubes T1 and T: arein their conductive conditions, the majorportion of the magnetic flux courses along the magnetic path whichincludes the arms I50 and Ilia, of the members I! and I8, shunt pieces11 and I8 and the included air gaps G1 and G2, the remaining portion ofthe magnetic flux continuing, along the path of low reluctance andinterlinking the primary and secondary windings.

Should the tube T1, for example, become grounded in operation, as by theformation of a conductive film of dirt, salt particles, matted insectbodies, snow, rain or the like, between its electrodes orbetween thehigh potential electrode. and the ground, the flow of current in thecircuit will reach about the same value as during normal operation ofthe tube. This is due to the peculiar magnetic shunt construction whichprovides protection from the flow of excessive current to eachindividual coil in the same manner as'the coil is protected fromexcessive current during ,normal operation. The same protection will beaiiorded where it is the coil S1 itself instead 01 the tube T1v whichbecomes grounded. As current begins to flow in the coil the main flux toseek a path of less reluctance. That path will be from the right handend of member I! through air gap G1, shunt piece l1,

arm lia, the lower part of member l5, member [4, and member l6 back, tomember l3. Due to the diversion of the major portion of the magneticflux from the coil S1, the current flowing through that coil undershort-circuit conditions will be limited to asafe value. Overheating ofthe coil and consequent charring of its insulation', therefore, isavoided.

1 Similarly, where the coil 8: or its tube '1': becomes grounded thecurrent flowing through coil S: will be limited to a safe value byvirtue of the diversion of the major portion of the magnetic flux fromthe coil S2 through the magnetic shunt path. The shunt path in thisinstance is that which includes the air gap G2, shunt piece l8 and armIto and the upper part of member it back to the'member l3.

Due to the magnetic shunt construction provided in my transformer, thecoils need be designed only for the maximum load current, since theshort-circuit current under all possibilities does not substantiallyexceed that value. As a result the transformer employs a finer wire thanordinarily used, the transformer is more. com.- pact. The magnetic fluxpaths are short and on the whole, the transformer is lighter in weightthan those heretofore known and used. Furtion of coil, 82 and tube T:will not be impaired because the main flux will continue to link coil 8:and to operate the tube '1: in the same manner as it does when thecircuit comprising coil 81 and tube T1 is operating normally. It will beunderstood that a like effect is had when the coil 32 isopen-circuited.- The coil Bi and its tube T1 will continue to operatenormally.

Ordinarily, in the design of a luminescent sign and display, thecomplete display is made ,up of a number of individual luminescent tubesor series of tubes of various configurations which are as near the samelength as is conveniently practicable. In energizing two tubescomprising a part of such a display, secondary windings of nrvtransformer apparatus are preferably of about the same voltage ratingsas a matter of convenience in production of the apparatus. Betterresults in operation are achieved where I the ratings of the secondarywindings conform the same length and cross-sectional area, andsame gaspressure, the shunt path comprising core piece I1 and air gap G1 is ofapproximately the same reluctance as the shunt path formed by shuntpiece II and air gap Ga. 1 This identity of reluctance of the shuntpaths is achieved by inserting the proper number of laminations in the.

shunt pieces l1 and II. It will be understood that where desired, thetubes T1 and '1': may be of different ratings. For example, the tube T1may be of higher resistance than the tube T2. In that event, the coil 81should have a greater number of turns of wire than the coil 82. Also,the shunt path formed by shunt piece I1 and air gap G1 should be ofhigher reluctance than the shunt path formed by shunt piece II and airgap Ga. This adjustment of the shunt path reluctances may convenientlybe made by inserting the proper number of laminations in the shuntpieces l1 and II.

.Itis -to be noted at this point that in my electrical transformerapparatus only a single primary winding and a single core structure areemployed. The total magnetic flux is created by the one primary windingand, by way of the single core structure, serves to link and energizeboth secondary windings. This construction, as

' and II! which are mentioned above, effects a direct saving in con- 1struction over heretofore known transformer ap paratus. It is to beparticularly noted, however, that these savings in iron, for the core,and wire and copper, for the primary winding, do not duced and the pathshave result in a loss in operating eiilciency nor, of greatestimportance, in a risk of damage to any secondary winding coil section asa result of accidental grounding of such a coil section. These savingsand economies in the construction of a single piece of apparatusrequiring but a single connection to a source of supply energy are ofthegreatest practical importance in the opera- .tion of a maximum lengthof luminescent tubing by a single piece of apparatus.

Moreover, it should be noted that my transformer apparatus isexceedingly compact and packing and shipping costs incident to thetransportation of a large number of the units is thus eil'ectivelyminimized.

Where desired, the highly beneficial operating characteristics of mytransformer apparatus are achieved by modifying the construction of theapparatus as by forming core member I, Ila and shunt II as an integralpiece and likewise .making it, its and Il of-integral construction. Thisconstruction of core members is shown in Fig. 2. Also my transformer maybe modified by mounting the secondary winding coil sections on the samelinear core member and by employing only a single primary 0611 sectionwhich is mounted on the other linear core member. Such a form ofconstruction is shown in Fig.2 of the drawing.

In Fig. 2, is shown a transformer llli which energizes a single tube Tand in turn is energized from a source I I2 of single phase alternatingcurrent electrical energy- The transformer is preferably enclosed casingH in Figure 1, but not shown in Figure 2 in a casing similar to the forthe sake of clarity in the drawing.

The core of" my transformer is formed by two parallel linear members Illand ill roughly p-shaped members H5 and I I l. The parts are heldtogether by steel core bands ill put in place while the parts are heldtogether under heavy pressure. Member H5 has a central arm Ilia whichextends parallel to the members III and Ill toward the center of thetransformer and terminates in a shunt portion Ill set at right angles tothe arm. Shunt portion llib extends toward member Ill, forming therewithan air gap G: of high magnetic reluctance. Similarly, member III has acentral arm 8a which extends parallel to the members H3 transformer 6b,set-at right angles to the arm. Shunt portion I lBb extends towardmember HI, forming therewith an air gap G4 of high magnetic reluctance.It will be noted that in this modification I have made the shuntportions lllb and 8b, integral with the rather than as parts sepa atetherefrom. Thus the number of Joints int e shunt paths is rehighpermeance except for the reluctance introduced by the air gaps G1 and(34. Moreover the integral form of constructionlends strength andrigidity to the core, shunt and the and Ill toward the center of. the Iand terminates in a shunt portion members Ill and II! teringinoperatio.

construction and minimizes or chat- The primary winding coil section Pofniy transformer is mounted on linear member H4. It is energizedthrough the leads HO and I" from source I l 2. The latter may be theordinary single phase 110 or 220 volt, 60-cycle commercial mains, or maybe any other suitable source. In my transformer there are two secondarywinding coil sections So and S4 which are con- I nected in series toform a single secondary winding. This winding energizes the tube Tthrough leads ill and I22 from one terminal of each of the coils So andS4 respectively. Th other ter- -mina.ls of the coils are grounded to thecore through metal strips I23 and I24 which are held in firm contactwith the core under the bands H1 and H8. The core itself is grounded asat low to maintain the gas in the tube T in an ionized condition and thetube becomes nonconductive and non-luminous. It remains in thiscondition until the secondary voltage again, during the next half cycleof primary E. M. F., reaches a value sumcient to ionize the gas in thetube. The tube thus becomes luminous 120 times per second where a 60cycle source of primary E. M. F. is used, and as before mentioned,'dueto H8. Because of the grounding of their one terminals to the groundedcore the output terminals of the high potential secondary winding 0. ilsections are limited to a safe value of poten l to ground. This is equalto the output potential of the one coil section to which the terminal isconnected. In no case may ,the'potential to ground amount to that olthecomplete secondary winding. This construction gives a direct saving ininsulation costs and maintains the possible value of potential to groundwithin safe limits and yet permits a desiredhigh value across the outputterminals of the transforiner apparatus.

In the operation of this transformer, as the I electromotfve forceimpressed across the terminals of the primary winding P by the source H2rises from a zero value, current begins to flow through the primarywinding. This current gencrates a magnetomotive force which causesmagnetic flux to course through the core in the counter-clockwisedirection, as indicated by the arrows in Fig. 2 of the drawing, during agiven half cycle of the applied E. M. This path is from, member H4through member H6, from right to left throughout the length of memberH3, and back through member H5 into member H4. The flux links thesecondary coil sections S: and S4 and induces in them an E. M. F. whosevalue depends on the density of the flux and the number. of turns ofwire in the coil sections. Since the two coil sections are connected inseries, their voltages are added so that the voltage across theterminals of the tube T is twice that developed persistence of vision itappearsto emit a steady glow of light.

' Should the tube T become short-circuited, as by the formation of aconductive film of moisture between its terminals, the current thenflowing through the secondary coils will not reach an excessive valuebecause of the peculiar magnetic. shunt construction provided. Ascurrent begins to flow between the terminals or the tube and 7 throughthe secondary-coils, a counter magnetomotive force is developed by thosecoils which causes the major portion of the main flux to follow a pathof high reluctance around and excluding the secondary coils as in normaloperation when the tube is ionized. This path is from member H4 into thelower part of member H6 and through arm H60, shunt portion H6b, air gapG4. the central portion of member H3, air gap Gs, shunt portion H5b, armH5a,and the lower part of member H5 back into member H4. The currentflowing when the tube is short-circuited, will be about the same as thatwhich courses through the tube when it" is operating normally, since theshort-circuit impedance is A about the same as the impedance when thetube is in its conductive condition. In neither case will the currentexceed a safe value.

by any one coil section and yet the maximum voltage to ground in anypart of the circuit is no more than that developed by one coil section.

When the voltage applied across the terminals of tube T reaches a valuesufliciently high to ionize the gas therein, the tube suddenly becomesconductive and luminous, current beginning to flow as soon as the gas isionized. This current does not reach an excessive value because of themagnetic shunt construction provided. As current flows through the coilsS3 and S4 it generates a magnetomotive force which opposes-the coursingof the main flux and causes the major portion of it to follow the pathsof high reluctance including the shunt members and their included airgaps. Thus, during the half cycle under consideration, while current isflowing through coils member H6, through arm Hlia, shunt portion I S:and S4, the major portion of the main flux courses from member H4 intoth lower part of l lib, air gap G4, the central part of member I I3,

air gap Ga, shunt portion i 15b, arm I l5a, and the lower part of memberH5 back into member H4.

This path excludes the coils S and S4 a minor' Where a single coilsection, say the coil Sa.

becomes grounded, as by the grounding of one terminal of the tube T, thecurrent flowing through that 6011 will not reach an unsafe value. Ascurrent begins to flow through the grounded coil 53, it causes a mfietomotive force to be developed by that coil opposing the coursing ofthe main flux and causing the major portion of it to seek a path of highreluctance around and excluding the coil S3. The path includes and linksthe coil .84 since no current flows in that coil, due to the potentialapplied to tube T being sufllcient to strike the tube, to. give rise toan opposing magnetomotive force. This path,

.ior the half cycle under consideration is frommember 4 through-memberm. the right half of member H3, air gap Gs, shunt portion H51), v

arm Illa and the lower part of member Hi back into member- I. Thevoltage generatedv condition of operation'exists when it is the coil"S4, rather than coil 83, which is grounded.

Where the whole secondary winding becomes open-circuited, as by thebreaking of the tube T,

no current will flow in the secondary circuit, since the construction ofmy transfer is such as to fully protect the secondary windings under allconditions damage to insulation is precluded, the

transformer withstanding the open-circuited Voltage without rupture ofinsulation.

Where desired, the primary winding can be made in two coil sectionsmounted on the lower parts of the members H and lit between arms IiiaandIlla and thebar Ill.

It will be understood that the coil sections S: and S4 may be connectedto two separate loads, instead of the single tube T. The coils S1 and S4may then be connected either in series, or, if theload mid-point isgrounded. in opposition. In that case the operation of the transformerwill be similar to that of the transformer illustrated in Figure l.

The transformer illustrated in Figure 2 is par-' ticul-arly economicalin construction. The single primary coil section P is cheaper inconstruction than are two separate .primary coil sections. Moreover, thecore members H5 and iii are identical in shape as are also the barmembers ill and Ill. Accordingly, only two dies are needed for thestamping of the core members. This effects a considerable saving becausedies are very expensive.

A saving is also effected in installation where my transformer is used.Only one transformer is needed to energize two short tubes orone longtube, whereas to meet the Undewriters requirements of maximum voltage toground two transformers have heretofore been required. A i'ixed laborcharge is made for each unit installed and, accordingly, by reducing thenumber of units, the cost of installation is reduced.

Thus it will be seen that there has been provided in this inventiontransformer apparatus in which the various objects hereinbefore noted,together with many practical advantages thereof, are successfullyachieved. It will be seen that my transformer apparatus isexceedinglycompact and rugged in construction and that it lends itself toinexpensive and emcient commercial production and installation,employing a minimum of different shaped core members and requiring aminimum of expensive dies, tools and equipment in its construction. Itwill be seen, further, that my transformer apparatus permits theenergization of a greater length of luminescent tubes than heretoforeknown transformer apparatus without at the same time encounteringexcessively high output potentials from terminals or conductors toground, or risking damage to the secondary windingstin the event ofaccidental grounding of either one or both coil sections of thesewindings.

As many possible embodiments may be made of my invention, and as manychanges may be made in the embodiments hereinbefore set forth. it'- willbe understood that all matter described here-- in, or shown in theaccompanying drawing is to be interpreted as illustrative, and not in alimiting sense.

I claim:

1. In electrical .transiormer apparatus of the character described, incombination, a core comprising two separate parallel linear core membersand two separate end core members interposed between saidlinear'members, including substan-, tially c-shaped portions, a primarywinding. com prising two coil sections one mounted on each of saidlinear members and two secondary windingcoii sections, also one mountedon each of said linear members, said two end core members forming withsaid linear members a closed main magnetic path interlinking saidprimary winding and said secondary winding coil sections and 7 asaavoswith said c-shaped portions also forming individual magnetic shunt pathsaround said secondary winding coil sections internally of said mainmagnetic path.

2. In electricaltransformer apparatus of the character described, incombination, a core comprising two separate parallel linear core membersand two separate and core members interposed between said linearmembers, each consisting of a c-shaped portion with a back extension, aprimary winding and two secondary winding coil sections mounted on saidcore, the toes and back extensions of said two end core members formingwith said linear members a closed main magnetic pathinterlinking saidprimary winding and said secondary winding coil sections and with saidO-shaped portions also forming magnetic shunt paths around saidsecondary windmounted on the other of said linear members,

the toes and back extensions of said end core members forming with saidlinear members a closed main magnetic path interlinging said primarywinding and said secondary winding coil sections and with said C-shapedportions facing each other and almost abutting the linear member onwhich said secondary coil sections are 'mounted ata point between thesame and forming individual magnetic shunt paths around said secondarywinding coil sections internally of said magnetic path with includedair-gaps.

4. In electrical transformer apparatus of the character described, incombination, two separate linear core members spaced in parallelrelationship, two separate core members, each having a portion sopositioned as to abut the near ends of said linear core members toeffect a closed magnetic circuit and each having a c-shaped portion sopositioned as to form a shunt path including air-gaps to at least one ofsaid linear members near the central portion thereof; a primary windingmounted on said linear core members; two secondary winding coil sectionsmounted on said linear core members linking said core members throughthe space provided between said members and the nearby c-shaped members;and separate binding means about the one near ends of the linear membersand each abutting core member for maintaining said core members in saidabutting relationship with minimum effect on said air-gaps.

5 In electrical transformer apparatusof the character described, incombination, two separate parallel linear core members, two separatecore members spaced apart and including 6- shaped portions cooperativelyassociated with said linear members effecting a closed magnetic circuittherewith by way of their one. portions and establishing shunt core pathincluding airgaps by way of their :c-shaped portions at points centrallyof said linear members, iron or steel clamping means at opposite ends ofsaid parallel members for holding together said linear core members andsaid members including c-shaped portions with minimum effect onsaidair-gaps, a primary winding mounted on said linear core members, andtwo secondary windings mounted on said linear core members and lyingwithin the I core members to effect a closed magnetic circuit and withthe c-shapedportions forming shunt paths including air-gaps with one orsaid linear members near the central portion thereof; two

secondary winding coil sections mounted on said one linear core memberand linking said core member through the space provided between saidmember and the nearby O-shaped core membars; a primary winding mountedon the other 01 said linear core members; separate. core bands about theone near ends of the linear members and each abutting core member formaintaining the whole in abutting relationship; and a steel casingsnugly fitting about the combination of said core members, windings andbands with the casing and core bands remote from the said airgaps.

CHARLES PHIUPPE BOUCHER.

